As of version 1.0.5.1 and later, StreetDeck now backs up all overwritten files when installing an update.
If after updating to a new version of StreetDeck, you want to revert back to a previous version, you can do so by going to Start | Run and enter
"C:\Program files\StreetDeck\SDUpdate.exe" -Restore
After running the program, a list of available backup versions will be shown, select one and choose OK. The version will be restored.
If you wish to undo the restore, just reinstall the update again.